Hello Chance,
Best wishes at building your empire! I am retired Army so I get where you are coming from. I want to be able to manage my investments from anywhere in the world. I enjoy travel a lot and have family in Korea and throughout the states. I also love to go back to Europe whenever I can.
I still work full time as a regional manager for a telecom company (was Signal Corps in the Army). Because I am busy I buy turnkey investments with a strong positive cash flow. The two I have locally in the Washington State JBLM area I manage myself but the rest for Indiana, Texas, Missouri and Tennessee I use local property managers and just manage the managers.
I use Quickbooks for my accounting and each property has it's own class to track income and expenses. The properties in each local area are held in an LLC set up in the state they are located in. I purchased a Quickbooks template from Landlord Accounting and have used it and the great instructions provided for many years.
http://landlordaccounting.com/
For the registered agents I pay up for three years at a time to get a discount and use Harbor Compliance.
https://www.harborcompliance.com/
I use Cozy for marketing, tenant applications, screening and to receive ACH rent payments direct to my business checking accounts.
https://cozy.co/for-landlords/tenant-screening/
If you manage your own rentals locally look for a good rental housing association that provides education in local landlord tenant law and forms that are prepared by a real estate attorney and updated regularly to comply with changes in law.
http://www.rhawa.org/
Also for marketing I use Zillow Rental Manager (formerly Postlets) to create effective ads that get posted to several sites and to create professional Craigslist ads.
https://www.zillow.com/rental-manager/posts/#/all/
I use Movoto to check up on the local schools and demographics of out of state properties I evaluate for purchase. Demographics can make or break your investment. Know that areas with a high number of single parent households and unusually high concentration of minority populations can be challenging and the areas do not appreciate well.
http://www.movoto.com/demographics/
I use this property analysis tool on my iPhone 6+ to track my properties but did not care for their accounting software when I tried it years ago. It may have improved since then.
http://www.propertyevaluator.com/
I use Neat Desk to scan all receipts and it can also be an effective accounting tool and could replace Quickbooks but is not as feature rich. I keep digital copies of all documents and receipts and shred all the paper. Back up, back up, back up.
http://www.neat.com/
Hope this helps!